Field of the Invention
The present invention relates to a sealing device, and more particularly to a sealing device having a sliding lip and a labyrinth lip. The sealing device according to the present invention is used, for example, as a hub bearing seal for a vehicle such as a motor vehicle, or is used as the other bearing seals (including the seal which is used for an industrial bearing).
Description of the Conventional Art
In the case that external foreign material (disturbance factor) such as water, muddy water, salt water, dust, brake fluid or oil is attached to a seal lip of a hub bearing seal which is installed to a bearing, the lip deforms by swelling of the rubber, and a sealing performance of the lip is lowered, in the conventional hub bearing seal. As a result, the conventional hub bearing has a defect that it is highly likely that the foreign material enters into the bearing.
In order to dissolve the defect mentioned above, there has been conventionally proposed a hub bearing seal which is provided with a sliding lip 71 sealing so as to prevent the foreign material in a bearing external portion (a machine outside) A from entering into a bearing internal portion (a machine inside) B, is provided with a labyrinth lip 72 in the machine outside A side of the sliding lip 71, and is structured such that the foreign material in the machine outside A is hard to reach the sliding lip 71 by the labyrinth lip 72, as shown in FIG. 3. According to the prior art in FIG. 3, since the swelling and deformation of the sliding lip 71 is suppressed at such a degree that the foreign material in the machine outside A is hard to reach the sliding lip 71, it is possible to improve the sealing performance. The labyrinth lip 72 is structured such that a labyrinth seal is formed by setting a micro gap in relation to the other member as its name suggests, and is constructed as a non-contact type lip in this manner so as to prevent a sliding torque from being increased by adding the lip.
However, in the prior art in FIG. 3, since the labyrinth lip 72 is exposed to the foreign material in the machine outside A in place of the sliding lip 71, the labyrinth lip 72 is swollen and deformed, and there is a risk that its function is lost in an early stage (the function is a function of protecting the sliding lip 71 by making the foreign material in the machine outside A hard to reach the sliding lip 71, this function being hereinafter called as “sliding lip protecting function” or simply called as “function”).